Publication

Critical thickness of GaN on AlN: impact of growth temperature and dislocation density

Nicolas Grandjean, Denis Martin, Pirouz Sohi
2017
Journal Articles

Abstract

Critical thickness and strain relaxation of c-plane GaN layers grown by molecular beam epitaxy on AlN were studied as a function of growth temperature and threading dislocation density (TDD). For this purpose we used AlN/sapphire templates and AlN single crystals with TDDs of similar to 10(9) cm(-2) and similar to 10(3) cm(-2), respectively. Whereas at high growth temperature (900 degrees C) the critical thickness for plastic relaxation is only 3 monolayers (MLs) for both substrates, this value drastically increases when decreasing the growth temperature. It reaches similar to 30 MLs when GaN is deposited at 750 degrees C on AlN single crystals. We also observed that the strain relaxation rate strongly depends on TDD. These results exemplify the lack of efficient gliding planes in III-nitrides when grown along the c-axis, which, combined with low kinetics, allows for plastic relaxation to be frozen out. Achieving pseudomorphic GaN layers on AlN is of interest for two-dimensional electron gases based on AlN/GaN/AlN heterostructures lattice-matched to AlN single crystal substrates.

Official source

https://infoscience.epfl.ch/entities/publication/9357d0a6-2ffc-4bb9-b6ba-bae0b2fe43a1

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Nicolas Grandjean, Denis Martin, Pirouz Sohi
2017
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/9357d0a6-2ffc-4bb9-b6ba-bae0b2fe43a1

About this result

Related concepts (29)

Gallium nitride

Gallium nitride () is a binary III/V direct bandgap semiconductor commonly used in blue light-emitting diodes since the 1990s. The compound is a very hard material that has a Wurtzite crystal structure. Its wide band gap of 3.4 eV affords it special properties for applications in optoelectronic, high-power and high-frequency devices. For example, GaN is the substrate which makes violet (405 nm) laser diodes possible, without requiring nonlinear optical frequency-doubling.

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Epitaxy (prefix epi- means "on top of”) refers to a type of crystal growth or material deposition in which new crystalline layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. The deposited crystalline film is called an epitaxial film or epitaxial layer. The relative orientation(s) of the epitaxial layer to the seed layer is defined in terms of the orientation of the crystal lattice of each material.

Molecular-beam epitaxy

Molecular-beam epitaxy (MBE) is an epitaxy method for thin-film deposition of single crystals. MBE is widely used in the manufacture of semiconductor devices, including transistors, and it is considered one of the fundamental tools for the development of nanotechnologies. MBE is used to fabricate diodes and MOSFETs (MOS field-effect transistors) at microwave frequencies, and to manufacture the lasers used to read optical discs (such as CDs and DVDs). Original ideas of MBE process were first established by K.

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